Turbine for tangential fan intended for being provided in a motor vehicle, tangential fan, ventilation device and heat-exchange module for a motor vehicle

ABSTRACT

The present invention relates to an impeller (102) for a tangential fan (100) intended to be fitted to a motor vehicle, the impeller extending chiefly in the direction of a longitudinal axis (L102) of the impeller (102), the impeller (102) having a plurality of blades (110) distributed in stages (112; 1121; 1122) along said longitudinal axis (L102) of the impeller (102), each stage (112; 1121; 1122) comprising a plurality of blades (110) angularly distributed about said longitudinal axis (L102) of the impeller (102), the blades (110) of each stage (112; 1121; 1122) of blades (110) preferably being equally angularly distributed about said longitudinal axis (L102) of the impeller (102), in which impeller the blades (110) of a first stage (1121) of blades (110) are angularly offset from the blades (110) of at least a second stage (1122) of blades (110).

The invention relates to an impeller for a tangential fan intended to equip a motor vehicle, and to a tangential fan equipped with such an impeller. The invention also relates to a ventilation device comprising such an impeller and to a heat-exchange module for a motor vehicle equipped with such a ventilation device.

A heat-exchange module (or cooling module) of a motor vehicle conventionally comprises a heat-exchange device and a ventilation device which is designed to generate a flow of air through the heat exchanger.

The heat-exchange device generally comprises tubes, known as heat-transfer tubes, arranged in rows and through which heat-transfer fluid circulates, and heat-exchange elements connected to these tubes, and often referred to as “fins”. The fins make it possible to increase the surface area for exchange between the tubes and the flow of air passing through the heat-exchange device.

The ventilation device increases the flow of ambient air passing through the heat-exchange device, making it possible to increase the exchange of heat between the heat-transfer fluid and the ambient air.

Such a ventilation device usually comprises a blower wheel, which has a number of disadvantages.

First of all, the assembly formed by the blower wheel and its drive system occupies a significant volume.

In addition, the distribution of the air blown by the blower wheel, which is often positioned in the middle of the row of heat-transfer tubes, is not uniform across the entire surface of the heat-exchange device. In particular, certain regions of the heat-exchange device, such as the ends of the heat-transfer tubes and the corners of the heat-exchange device, receive little, if any, of the flow of air blown by the blower wheel.

Finally, when there is no need to switch on the ventilation device, notably when the flow of ambient air created by the movement of the motor vehicle is enough to cool the heat-transfer fluid, the blades of the blower wheel partially mask the heat-exchange device. Thus, part of the heat-exchange device is ventilated little, if at all, by the flow of ambient air in this case, and this limits the exchange of heat between the heat-exchange device and the flow of ambient air.

Moreover, a cooling module is known, for example from application EP-A-0233174, that comprises a tangential fan blowing air over a heat-exchange device which, in this case, is arranged horizontally. However, the cooling module described in that application has a sizeable bulk, notably owing to the fact that the impeller of the tangential fan is large in size in order to ensure satisfactory flow of air over the heat-exchange device. Furthermore, such a cooling module is also noisy.

Application JP-A-2001214740 describes a cooling module in which two tangential fans are used to draw air through a heat-exchange device. This module is therefore likewise bulky.

It is an object of the invention to improve the known cooling modules still further.

To this end, one subject of the invention is an impeller for a tangential fan intended to be fitted to a motor vehicle, the impeller extending chiefly in the direction of a longitudinal axis of the impeller, the impeller having a plurality of blades distributed in stages along said longitudinal axis of the impeller, each stage comprising a plurality of blades angularly distributed about said longitudinal axis of the impeller, the blades of each stage of blades preferably being equally angularly distributed about said longitudinal axis of the impeller, in which impeller the blades of a first stage of blades are angularly offset from the blades of at least a second stage of blades.

Thus, advantageously, the phenomena of resonance which may occur when all the blades are aligned, something which may give rise to simultaneous noises that add to one another, are limited, or even avoided. In addition or as an alternative, this makes it possible to shift the resonant frequencies, advantageously into a frequency band that is not audible or which is perceived as less annoying.

As a preference, the impeller according to the invention comprises one or more of the following features, considered alone or in combination:

the blades of the first stage of blades are angularly offset from the blades of the two stages of blades neighboring said first stage of blades;

the blades of each first stage of blades are angularly offset from the blades of the two stages of blades neighboring each first stage of blades;

the blades of the first stage of blades are angularly offset from the blades of the at least one second stage of blades by an angular offset corresponding to the thickness of the blades of the first stage of blades and/or of the second stage of blades;

the blades of the first stage of blades are angularly offset from the blades of the at least one second stage of blades by an angular offset equal to half the angular spacing between the blades of the first stage of blades and/or of the at least one second stage of blades;

the blades of said first stage of blades are angularly offset from all the blades of all the other stages of blades;

the blades of each stage of blades are angularly offset from all the blades of all the other stages of blades;

According to another aspect, the invention relates to a tangential fan intended to be fitted to a motor vehicle comprising a blower housing defining a substantially cylindrical housing, an electric motor and an impeller as described hereinabove in all its combinations, housed in the substantially cylindrical housing and designed to be driven in rotation by the electric motor.

The invention further relates to a ventilation device for a motor vehicle, particularly for a motor vehicle heat-exchange system, comprising a tangential fan as described hereinabove, in all its combinations, and a plurality of tubes able to be supplied with air flow by the tangential fan.

Advantageously, each tube of the plurality of tubes has at least one ejection opening for a flow of air passing along the tube.

Furthermore, the ventilation device according to the invention preferentially comprises one or more of the following features, taken alone or in combination:

the tubes are substantially rectilinear, and aligned in such a way as to form a row of tubes;

the opening is a slot in an external wall of the duct, the slot extending in a direction of elongation of the duct, preferably over at least 90% of the duct length and/or the height of said at least one opening is greater than or equal to 0.5 mm, preferably greater than or equal to 0.7 mm, and/or less than or equal to 2 mm, preferably less than or equal to 1.5 mm;

each tube, over at least one portion, has a geometric section comprising:

-   -   a leading edge;     -   a trailing edge opposite to the leading edge;     -   a first and a second profile, each extending between the leading         edge and the trailing edge,

said at least one opening of the duct being on the first profile, said at least one opening being configured in such a way that the ejected flow of air flows along at least part of the first profile,

said at least one opening of the first profile is delimited by an external lip and an internal lip, one end of the internal lip being extended, in the direction of the second profile, beyond a plane normal to the free end of the external lip;

the maximum distance between the first and the second profiles, in a direction of alignment of the tubes, is downstream of said at least one opening, in the direction in which said flow of air ejected by said at least one opening flows, the maximum distance preferably being greater than or equal to 5 mm, preferably greater than or equal to 10 mm, and/or less than or equal to 20 mm, preferably less than or equal to 15 mm, the maximum distance even more preferably still, being equal to 11.5 mm;

the first profile comprises a convexly curved part of which the vertex defines the point of the first profile that corresponds to the maximum distance, the convexly curved part being positioned downstream of the opening in the direction in which said flow of air ejected by said at least one opening flows;

the first profile comprises a first substantially rectilinear part, preferably downstream of the convexly curved part in the direction in which said flow of air ejected by the at least one opening flows, wherein the second profile comprises a substantially rectilinear part, preferably extending over the majority of the length of the second profile, the first rectilinear part of the first profile and the rectilinear part of the second profile forming a non-flat angle, the angle preferably being greater than or equal to 5°, and/or less than or equal to 20°, and more preferably still, equal to 10°;

the first rectilinear part extends over a portion of the first profile corresponding to a length, measured in a direction perpendicular to the direction of alignment of the ducts and to a longitudinal direction of the ducts, that is greater than or equal to 30 mm, preferably greater than or equal to 40 mm, and/or less than or equal to 50 mm;

the first profile comprises a second rectilinear part, downstream of the first rectilinear part in the direction in which the flow of air ejected by the at least one opening flows, the second rectilinear part extending substantially parallel to the rectilinear part of the second profile, the first profile preferably comprising a third rectilinear part, downstream of the second rectilinear part of the first profile, the third rectilinear part forming a non-flat angle with the rectilinear part of the second profile, the third rectilinear part extending substantially as far as a rounded edge that connects the third rectilinear part of the first profile and the rectilinear part of the second profile, the rounded edge defining the trailing edge of the profile of the duct;

the distance between the second rectilinear part of the first profile and the rectilinear part of the second profile is greater than or equal to 2 mm and/or less than or equal to 10 mm, preferably less than or equal to 5 mm;

said geometric section of the duct has a length, measured in a direction perpendicular to the direction of alignment of the tubes and to a main direction of extension of the tubes, that is greater than or equal to 50 mm, and/or less than or equal to 70 mm, preferably substantially equal to 60 mm;

the ventilation device comprises at least a first and a second tube, the first profile of the first duct facing the first profile of the second duct;

the ventilation device further comprises a third tube, such that the second profile of the second tube faces the second profile of the third tube, the distance between the center of the geometric section of the second tube and the center of the geometric section of the third tube preferably being less than the distance between the center of the geometric section of the first tube and the center of the geometric section of the tube; and

each tube is symmetrical with respect to the plane containing the leading edge and the trailing edge, such that each duct comprises two symmetrical openings, on the first profile and on the second profile, respectively.

Finally, according to another aspect, the invention relates to a cooling module for a motor vehicle comprising a heat-exchange device and a ventilation device as described hereinabove, in all combinations thereof, designed to create a flow of air through the heat exchanger.

The invention will be better understood, and other aims, details, features and advantages thereof will become more clearly apparent from the following detailed explanatory description of embodiments of the invention, which are provided by way of a purely illustrative and non-limiting example, with reference to the appended schematic drawings. In these drawings:

FIG. 1 is an exploded schematic view of a motor vehicle cooling module;

FIG. 2 schematically depicts part of the ventilation device of the cooling module of FIG. 1;

FIGS. 3 and 4 schematically depict a detail of two variants of the ventilation device of FIG. 2;

FIG. 5 is a perspective view of one example of an impeller that can be used in a ventilation device according to FIG. 3 or 4;

FIG. 5 schematically depicts a longitudinal section through the fan of FIG. 2, equipped with the reduction device of FIG. 4;

FIG. 6 is a front view of a detail of the impeller of FIG. 5;

FIG. 7 schematically depicts a superposition of views in section on planes A-A and B-B of FIG. 6;

FIG. 8 schematically depicts a front view of a detail of a variant of the impeller of FIG. 5;

FIG. 9 schematically depicts a superposition of views in section on planes D-D and E-E of FIG. 8;

FIG. 10 is a perspective view of part of the heat-exchange module of FIG. 1 in section on a transverse plane;

FIG. 11 is a view in transverse section of part of the heat-exchange module of FIG. 1;

FIG. 12 is a view in transverse section of a first example of an aerodynamic tube used in the heat-exchange module of FIG. 1;

FIGS. 13 to 15 illustrate in transverse section other examples of aerodynamic tubes that can be used in the heat-exchange module of FIG. 1; and

FIG. 16 is a view in transverse section of an example of a ventilation tube that can be used in the heat-exchange module of FIG. 1.

In the remainder of the description, elements that are identical or perform identical functions bear the same reference sign. In the present description, for the sake of conciseness these elements are not described in detail within each embodiment. Rather, only the differences between the embodiment variants are described in detail.

FIG. 1 depicts a first example of the heat-exchange module 10 with a heat exchanger 1, intended to be fitted to a motor vehicle, associated with a ventilation device 2.

The heat exchanger 1 comprises heat-transfer ducts 4 in which fluid, in this instance water or liquid coolant, is intended to circulate. The heat-transfer ducts 4 are substantially rectilinear here and extend in a longitudinal direction. The heat-transfer ducts thus form heat-transfer tubes 4. The heat-transfer tubes 4 are mutually parallel and aligned to form a row. The heat-transfer tubes 4 are substantially all the same length.

The heat-transfer ducts 4 each extend between a fluid inlet header 5 and a fluid outlet header 7 which headers are common to all the heat-transfer ducts 4. As a preference, the orifices of the fluid inlet header 5, into which orifices the heat-transfer ducts 4 open, are all comprised in the one same first plane. As a preference, the orifices of the fluid outlet header 7, into which orifices the heat-transfer ducts 4 open, are all comprised in the one same second plane, preferably parallel to said first plane.

More specifically, and in a way that is conventional in motor vehicle heat exchangers, each heat-transfer tube 4 has a substantially oblong cross section and is delimited by first and second planar walls which are connected to heat-exchange fins 6 (see FIGS. 10 and 11). For the sake of clarity, the fins are not depicted in FIG. 1.

The heat-exchange module 10 also comprises a ventilation device 2 comprising a plurality of ventilation ducts 8. The ventilation ducts 8, just like the heat-transfer ducts 4, are substantially rectilinear, so as to form ventilation tubes 8. The heat-transfer tubes 8 are also mutually parallel and aligned to form a row of ventilation tubes 8. The ventilation tubes 8 are also the same length. The length of the ventilation tubes 8 is, for example, substantially equal to the length of the heat-transfer tubes 4.

The ventilation device 2 is intended to generate a flow of air toward the heat-transfer tubes 4.

The heat-transfer tubes 4 and the ventilation tubes 8 may all be mutually parallel, as has been illustrated in FIG. 1. In this way, the rows of ventilation tubes 8 and of heat-transfer tubes 4 are themselves parallel. Further, the ventilation tubes 8 may be arranged in such a way that each of them faces a heat-transfer tube 4.

The number of ventilation tubes 8 is tailored to suit the number of heat-transfer tubes 4. For example, for a conventional heat exchanger 1, the ventilation device 2 may comprise for example at least ten ventilation tubes 8, preferably at least fifteen ventilation tubes 8, more preferably still, at least twenty-four ventilation tubes 8 and/or at most fifty ventilation tubes 8, preferably at most thirty-six ventilation tubes 8, more preferably still, at most thirty ventilation tubes 8. The heat exchanger 1 may, for example, comprise between sixty and seventy heat-transfer tubes 4.

The ventilation tubes 8 and number of such tubes of the ventilation device 2 may be such that a minimum cross section for the passage of air between the tubes of the ventilation device, as defined in a plane substantially perpendicular to the flow of air through the heat exchanger 1, is comprised between 25 and 50% of the surface area, defined in a plane perpendicular to the flow of air through the heat exchanger, between two ends-extremity heat-transfer tubes.

As a preference, the frontal surface area of the ventilation tubes 8, measured in a plane substantially perpendicular to the flow of air passing through the heat exchanger 1, is less than 85% of the frontal surface area occupied by the heat-transfer tubes 4.

Furthermore, in order to limit the volume occupied by the heat-exchange module 10 comprising the heat exchanger 1 and the ventilation device 2, while at the same time obtaining heat-exchange performance similar to that of a blower-wheel type of ventilation device, the row of ventilation tubes 8 may be arranged at a distance less than or equal to 150 mm from the row of heat-transfer tubes 4, preferably less than or equal to 100 mm This distance is preferably greater than or equal to 5 mm, preferably greater than 40 mm This is because too short a distance between the ventilation tubes 8 and the heat-transfer tubes 4 carries the risk of not allowing uniform mixing of the flow of air ejected from the ventilation tubes 8 with the induced flow of air. Mixing that is not uniform means that the heat-transfer tubes 4 cannot be cooled uniformly and leads to high pressure drops. Too great a distance carries the risk of not allowing the assembly formed by the ventilation device and the heat-exchange device to be installed in a motor vehicle without the need to adapt the design of the propulsion unit and/or of the other parts of the motor vehicle present in the vicinity of the heat-exchange module accordingly.

Furthermore, in order to limit the volume occupied by the heat-exchange module, steps can be taken to ensure that the height of the row of ventilation tubes 8 (the term height referring here to the dimension corresponding to the direction in which the ventilation tubes 8 are aligned) is substantially equal to or less than that of the height of the row of heat-transfer tubes 4. For example, if the height of the row of heat-transfer tubes 4 is 431 mm, steps can be taken to ensure that the height of the row of ventilation tubes 8 is substantially equal to or less than this value.

In the example illustrated in FIGS. 1 to 2, the ventilation device 2 further comprises a supply device supplying the ventilation tubes 8 with air via an air inlet header 12. In this particular instance, the ventilation device 2 comprises two air inlet headers 12 arranged respectively at a longitudinal end of the ventilation tubes 8. A tangential fan 100 is arranged inside each air inlet header 12. More particularly, the impeller 102 of such a tangential fan 100 is arranged inside each inlet header 12, which inlet header 12 acts as the blower housing of the tangential fan 100. Each air inlet header 12 may for example be tubular. In the embodiment of FIG. 2, the air inlet headers 12 extend in the one same longitudinal direction L102, which in this instance is perpendicular to the direction of elongation (or longitudinal direction) of the heat-transfer tubes 4 and ventilation tubes 8. Thus, each inlet header 12 defines a substantially cylindrical housing accommodating the impeller 102, the housing being of axis parallel to the longitudinal direction L102 of the impeller 102. The impeller 102 is free to rotate in the air inlet header 12, about the axis of the housing formed in the air inlet header 12 concerned. The motor for the tangential fan 100 may be housed in a base 104 of the air inlet header 12. The fluidic communication between the housing accommodating the impeller 102 and the base 104 of the air inlet header may be limited or even interrupted, in order to avoid air leaks.

As may be seen notably from FIGS. 1 to 4, the air inlet header 12 comprises a plurality of air ejection orifices 14, each air ejection orifice 14 being connected to a single ventilation tube 8, and more specifically to the end of the ventilation tube 8. Thus, each ventilation tube 8 opens into a distinct orifice 14 of each header 12. Thus, each air header 12 has as many orifices 14 as it accepts ventilation tubes 8, one ventilation tube 8 being accommodated in each of the orifices 14 of the air header 12. This allows a more uniform distribution of the flow of air passing through each air header 12, in the various ventilation tubes 8.

Furthermore, in the example of FIG. 3, the housing that accommodates the impeller 102, is open to the outside by a longitudinal slot 106 extending over substantially the entire length of the housing formed by the air inlet header 12 accommodating the impeller 102. This allows exterior air to be drawn in by the rotating impeller 102, the air inlet header 12 guiding this drawn-in air toward the ventilation tubes 8.

In the variant of FIG. 4, the housing accommodating the impeller 102 has an opening 108 at its opposite longitudinal end to the base 104 of the air inlet header 12. Of course, other shapes and positions of opening are conceivable, allowing the exterior air to be drawn in by means of the fan 100.

Advantageously, each air header 12 has no opening other than the orifices 14 and the slot 106 or the opening 108, respectively. In particular, the header 12 preferably has no opening oriented in the direction of the heat exchanger 1, which might, in this instance, allow part of the flow of air created in the air header 12 to be ejected directly toward the heat exchanger 1 without passing along at least a portion of a ventilation tube 8. Thus, all of the flow of air created by the fan or fans 100 in the air inlet header 12 passes along the air header or headers 12 to be distributed between substantially all of the ventilation tubes 8. This also allows this flow of air to be distributed more uniformly.

A first example of an impeller 102 of the fan 100 is illustrated in FIGS. 5 to 7.

As may be seen from FIG. 5, the impeller 102 comprises a plurality of blades 110 (or vanes) distributed in stages 112 along the longitudinal axis L102 of the impeller 102. The longitudinal axis L102 of the impeller corresponds to its axis of rotation when driven by the motor of the fan 100. In the example illustrated, the impeller 102 comprises thirteen stages 112 of blades 110. Of course, this number of stages 112 is nonlimiting.

As a preference, the blades 110 of a stage 112 are equally angularly distributed about the longitudinal axis L102. In the example illustrated, all the stages 112 have the same number of blades 110. Also, all the blades 110 of the various stages 112 are identical here.

However, as is apparent from FIGS. 6 and 7, the blades 110 of a first stage 112 ₁ are angularly offset about the longitudinal axis L102 of the impeller 102 with respect to the blades 110 of the second stage 112 ₂. In the example illustrated, the first stage 112 ₁ and the second stage 112 ₂ are neighboring, in this instance adjacent, in the longitudinal direction of the impeller 102. However, it should be noted that the first and second stages 112 ₁ and 122 ₂ of blades may be separated by one or more stages 112 of blades 110 and/or by a portion of the impeller 102 that has no blades 110 and that for example forms a shaft portion intended to guide the rotation of the impeller 102 in the housing of the air inlet header 12. As visible in FIGS. 6 and 7, in this particular instance, the angular offset between the blades 110 of the first stage 112 ₁ and the blades of the second stage 112 ₂ is equal to half the angular spacing between two blades 110 of the one same stage 112.

This then avoids all the blades 110 of the impeller 102 being aligned, as this would carry the risk of generating considerable noise, particularly because of the fact that all the blades work in synchrony. By offsetting the blades 110 it is possible to ensure, rather, that the blades 110 work in separate groups, and this makes it possible to reduce the noise generated.

In particular, in the example of FIGS. 5 to 7, the blades 110 of each stage 112 may be offset by half the spacing between the blades, with respect to each of the two neighboring stages. Thus, a first half of the stages 112 of blades 110 have blades 110 which are aligned with one another and which are offset by half the angular spacing between the blades 110 with respect to the blades 110 of the other half of the stages 112. The noise generated by the rotating impeller 102 can thus be substantially halved, which corresponds to a reduction by the order of 3 dB in the noise emitted.

In the case of the impeller 102 depicted in FIGS. 8 and 9, however, the angular offsetting of the blades 110 between two neighbouring stages 112 ₁, 112 ₂ corresponds to the thickness of a blade 110.

Alternatively or in addition, the spacing between the blades 110 may be divided into substantially as many intermediate positions as there are stages 112 of blades 110. Thus, the blades 110 of the various stages 112 may be offset step-by-step in the same angular direction, along a longitudinal direction. The blades of the various stages therefore extend substantially in a helix along the various stages 112 of blades 110. In this particular case, all the blades 110 of all the stages 112 are offset with respect to all the blades 110 of all the other stages 112. This allows an even greater reduction in the noise generated by the rotating impeller 102.

Of course, numerous other configurations are accessible to those skilled in the art, allowing all the blades 110 of all the stages 112 to be offset with respect to all the other blades 110 of all the other stages 112. In particular, based on the preceding configuration in which the blades 110 of the various stages 112 extend in the manner of the helix, it is possible to swap the various stages around, without altering their orientation about the longitudinal axis L102 of the impeller 102.

Furthermore, as illustrated in FIG. 16, each ventilation tube 8 has one or several openings 16 for the passage of a flow of air passing along the tube 8. The openings 16 of the ventilation tubes 8 are situated on the outside of the air headers 12. The openings 16 may be oriented substantially in the direction of the heat exchanger 1 and, more specifically still, substantially in the direction of the heat-transfer tubes 4, the openings being arranged for example facing the heat-transfer tubes 4 or the fins housed between the heat-transfer tubes.

Thus, the air header or headers 12 and the ventilation tubes 8 are configured here in such a way that a flow of air created in the air header or headers 12 by one or more fans 100 is distributed between the various ventilation tubes 8, travels along the various ventilation tubes 8, and is ejected through the openings 16. Since the openings 16 are positioned facing the heat exchanger 1, a flow F2 of air is ejected via the openings 16 and passes through the heat exchanger 1.

It should be noted, however, that the flow F1 of air passing through the heat exchanger 1 may be substantially different than the flow F2 of air ejected via the openings. In particular, the flow F1 of air may comprise, in addition to the flow F2 of air, a flow of ambient air created by the movement of the motor vehicle while it is running

In the example illustrated in FIG. 16, the ventilation tubes 8 have a substantially oblong transverse section, interrupted by the openings 16.

Choosing this shape allows for easy manufacture of the ventilation tubes 8 and gives the ventilation tubes 8 good structural integrity. In particular, such ventilation tubes 8 may be obtained by bending an aluminum sheet for example, but also by molding, overmolding or by three-dimensional printing in metal or in plastic.

More specifically, according to this example depicted in FIG. 16, the transverse section of the ventilation tubes 8 has a substantially elliptical shape of which the minor axis corresponds to the height of the ventilation tubes 8 and the major axis to the width of the ventilation tubes 8 (the terms height and width being intended to be understood as being with respect to the orientation in FIG. 16). For example, the minor axis h of the ellipse measures around 11 mm.

In order to increase the flow F2 of air ejected toward the heat exchanger 1 through the openings 16, the openings 16 consist of slots made in the wall 17 of the ventilation tube 8, these slots 16 extending in the direction of elongation of the ventilation tube 8. This slotted shape makes it possible to form an air passage of large dimensions, while at the same time maintaining satisfactory structural integrity of the ventilation tubes 8. Thus, in order to obtain the largest possible air passage, the openings 16 extend over a large proportion of the length of the ventilation tube 8, preferably over a total length corresponding to at least 90% of the length of the ventilation tube 8.

As may be seen in FIG. 16, the openings 16 are delimited by guide lips 18 projecting from the wall 17 of the ventilation tube 8.

Because they project from the wall 17 of each ventilation tube 8, the guide lips 18 are able to guide the air ejected by the opening 16 from the inside of the ventilation tube 8 toward the heat exchanger 1.

The guide lips 18 are preferably planar and substantially parallel. For example, they are spaced apart by a distance of around 5 mm, and have a width (the term width being intended to be considered with respect to the orientation of FIG. 16) of between 2 and 5 mm The guide lips 18 advantageously extend over the entire length of each opening 16.

The guide lips 18 are preferably formed as one with the ventilation tube 8. The guide lips 8 are, for example, obtained by bending the wall 17 of the ventilation tube 8.

Furthermore, the openings 16 are also delimited, in the length direction of the ventilation tubes 8, by reinforcing elements 20 of the ventilation tubes 8. The reinforcing elements 20 allow the width of the openings 16 to be kept constant. In this instance, this is achieved through the fact that the reinforcing elements extend between the two guide lips 18 that extend on either side of each opening 16. The reinforcing elements 20 preferably extend in a plane substantially normal to the direction of elongation of the ventilation tubes 8, this being so as to keep the section of the openings 16 that allow for the passage of the flow F2 of air as large as possible. The reinforcing elements 20 are advantageously uniformly distributed along the length of the ventilation tubes 8. Each ventilation tube 8 may for example comprise seven reinforcing elements 20. Of course, this number is entirely nonlimiting.

According to variants which have not been illustrated, the transverse section of the ventilation tubes 8 is substantially circular, interrupted by the openings 16. For example, the diameter of the circle interrupted by the openings 16 is around 11 mm.

In addition, in these variants, the guide lips 18 extend in part inside the ventilation tubes 8. As a preference, the guide lips 18 extend inside the ventilation tubes 8 over half of their width. For example, if the guide lips 18 have a width of 4 mm, the part extending inside the ventilation tube 8 has a width of 2 mm.

According to yet another variant, each guide lip 18 is associated with an obstructing wall, which connects the end of the guide lip 18 extending inside the ventilation tubes 18 to the internal face of the wall 17 of the ventilation tube. This obstructing wall thus makes it possible to limit the phenomenon of recirculation of air in the space comprised between the guide lip 18 and the internal face of the wall 17 of the ventilation tube 8.

The obstructing wall may for example be planar and extend from the guide lip 18, viewed in transverse section, perpendicularly with respect to the guide lip 18. The volume contained between the obstructing wall and the internal face of the wall 17 of the ventilation tube may be filled with foam, a plastic or metal casing, or else with any other material, preferably lightweight.

Another example of ventilation tubes 8 will now be described in greater detail with reference to FIGS. 10 to 12. In what follows, the ventilation tubes 8 are referred to as aerodynamic tubes 8. It may be noted here that the shape of the ventilation tubes 8 is theoretically independent of the configuration of the air inlet headers and of the fan 100 that they include.

An aerodynamic tube 8 has, over at least a portion, preferably over substantially the entirety, of its length, a transverse section as illustrated in FIG. 12 having a leading edge 37, a trailing edge 38 opposite to the leading edge 37 and, in this instance, positioned facing the heat-transfer tubes 4, and a first and second profile 42, 44, each extending between the leading edge 37 and the trailing edge 38. The leading edge 37 is defined for example as being the point at the front of the section of the aerodynamic tube 8 where the radius of curvature of the section is minimal. The front of the section of the aerodynamic tube 8 may, for its part, be defined as being the portion of the section of the aerodynamic tube 8 which is on the opposite side from—that is to say not facing—the heat exchanger 1. Likewise, the trailing edge 38 can be defined as being the point at the rear of the section of the aerodynamic tube 8 where the radius of curvature of the section is minimal. The rear of the section of the aerodynamic tube 8 may, for example, be defined as being the portion of the section of the aerodynamic tube 8 which is facing the heat exchanger 1.

The distance c between the leading edge 37 and the trailing edge 38 is for example between 16 mm and 26 mm. This distance here is measured in a direction perpendicular to the direction of alignment of the row of aerodynamic tubes 8 and to the longitudinal direction of the aerodynamic tubes 8.

In the example of FIG. 12, the leading edge 37 is free. In this figure likewise, the leading edge 37 is defined on a parabolic portion of the section of the aerodynamic tube 8.

The aerodynamic tube 8 illustrated in FIGS. 10 to 12 also comprises at least one opening 40 for ejecting a flow of air passing along the aerodynamic tube 8, outside the aerodynamic tube 8 and outside the air inlet header 12, notably substantially toward the heat exchanger 1. The opening or each opening 40 is, for example, a slot in an external wall 41 of the aerodynamic tube 8, the slot or slots extending for example in the direction of elongation of the aerodynamic tube 8 in which they are made. The total length of the opening 40 or of the openings may be greater than 90% of the length of the aerodynamic tube. Each opening 40 is distinct from the ends of the aerodynamic tube 8, via which ends the aerodynamic tube 8 opens into an air header 12. Each opening 40 is also outside of the air inlet header 12. The slotted shape makes it possible to form a large-sized air passage toward the heat exchanger 1 without excessively reducing the mechanical strength of the aerodynamic tubes 8.

In what follows, just one opening 40 is described, it being understood that each opening 40 of the aerodynamic tube 8 may be identical to the opening 40 described.

The opening 40 is arranged for example in the vicinity of the leading edge 37. In the example of FIG. 12, the opening 40 is on the first profile 42. In this example, the second profile 44 has no opening 40. The opening 40 in the first profile 42 is configured so that the flow of air ejected via the opening 40 flows along at least part of the first profile 42.

The aerodynamic tubes 8 of the ventilation device 2 may be oriented with the first profile 42 or the second profile 42 oriented upward, alternately, as illustrated in FIGS. 10 and 11. Thus, alternately, two neighboring aerodynamic tubes 8 are such that their first profiles 42 face one another or, on the other hand, their second profiles 44 face one another. The distance between two neighboring aerodynamic tubes 8 of which the second profiles 44 face one another is less than the distance between two neighboring aerodynamic tubes 8 of which the first profiles 42 face one another. The spacing between two neighboring aerodynamic tubes or the distance between the center of the geometric section of a first aerodynamic tube 8 and the center of the geometric section of the second aerodynamic tube 8, when the tubes are such that the first profile 42 of the first aerodynamic tube 8 faces the first profile 42 of the second aerodynamic tube 8, measured in the direction of alignment of the aerodynamic tubes 8 is greater than or equal to 15 mm, preferably greater than or equal to 20 mm, and/or less than or equal to 30 mm, preferably less than or equal to 25 mm.

For each pair of aerodynamic tubes 8 of which the openings 40 face one another, the air flows each ejected by these openings 40 thus create a passage of air into which, a part, referred to as induced air, of the ambient air is entrained through suction.

It should be noted here that the flow of air ejected by the openings 40 closely follows at least a part of the first profile 42 of the aerodynamic tube 8, for example as a result of the Coanda effect. Using this phenomenon to advantage, it is possible, thanks to the entrainment of the ambient air in the air passage created, to obtain an air flow rate sent toward the heat-transfer tubes that is identical to that generated by a blower-wheel fan, but for a lower energy consumption.

Specifically, the flow of air sent toward the row of heat-transfer tubes 4 is the sum of the flow of air ejected by the slots and of the induced air. Thus it is possible to operate one or more fans that are lower in power in comparison with a conventional blower-wheel fan generally employed in the context of such a heat-exchange module.

A first profile 42 having a Coanda surface also means that the openings 40 do not have to be oriented directly toward the heat-transfer tubes 4, and this therefore means that the amount of space taken up by the aerodynamic tubes 8 can be limited. It is thus possible to maintain a greater passage section between the aerodynamic tubes 8, this being something that encourages the formation of a higher induced-air flow rate.

The opening 40 is, in FIG. 12, delimited by lips 40 a, 40 b. The separation e between the lips 40 a, 40 b, which defines the height of the opening 40, may be greater than or equal to 0.3 mm, preferably greater than or equal to 0.5 mm, more preferably still, greater than or equal to 0.7 mm and/or less than 2 mm, preferably less than or equal to 1.5 mm, more preferably still, less than 0.9 mm, and as an even greater preference, less than or equal to 0.7 mm The height of the slot is the dimension of this slot in the direction perpendicular to its length. The smaller the height of the slot 40, the higher the velocity of the flow of air ejected via this slot. A high ejected air-flow velocity results in a high dynamic pressure. This dynamic pressure is then converted into a static pressure in the mixing zone in which the flow of air ejected by the slots 40 mixes with the induced flow of air. This static pressure makes it possible to overcome the pressure drops caused by the presence of the heat exchanger downstream of the ventilation device, so as to ensure a suitable flow of air through the heat exchanger. These pressure drops caused by the heat exchanger vary notably according to the spacing of the heat-exchange tubes and the spacing of the fins of the heat exchanger, and according to the number of heat-exchange modules that may be superposed in the heat exchanger. However, too small a slot height leads to high pressure drops in the ventilation device, necessitating the use of one or more over-rated air propulsion device(s). This may result in additional cost and/or create a space requirement that is incompatible with the amount of space available in the vicinity of the heat-exchange module within the motor vehicle.

The outer lip 40 a here consists of the extension of the wall of the aerodynamic tube 8 defining the leading edge 37. The inner lip 40 b consists of a curved part 50 of the first profile 42 (see FIG. 12). One end 51 of the internal lip 40 b may continue, as illustrated in FIG. 11, toward the second profile 44, beyond a plane L normal to the free end of the external lip 40 a. In other words, the end 51 of the internal lip 40 b may continue, in the direction of the leading edge 37, beyond the plane L normal to the free end of the outer lip 40 a. The end 51 may therefore contribute to directing the flow of air circulating in the aerodynamic tube 8 toward the opening 40.

As illustrated in FIG. 10, the opening 40 of the aerodynamic tube 8 may thus be configured in such a way that a flow F of air circulating in this aerodynamic tube 8 is ejected via this opening 40 such that it flows along the first profile 42 substantially as far as the trailing edge 38 of the aerodynamic tube 8. The flowing of the flow F of air along the first profile 42 may be the result of the Coanda effect. It will be recalled that the Coanda effect is an aerodynamic phenomenon that results in the fact that a fluid, flowing along a surface at a short distance therefrom, has a tendency to hug or even attach to said surface.

In addition, this flow F of air flowing along the first profile gives rise to an induced air flow I in the passage 46 between two aerodynamic tubes 8, the induced air flow I corresponding to a portion of the flow of ambient air A drawn in between the two aerodynamic tubes as a reaction to the flow F of air along the first profile 42.

In order to achieve this, in this instance, the maximum distance h between the first 42 and the second 44 profiles, as measured in a direction of alignment of the aerodynamic tubes 8, is downstream of the opening 40. The maximum distance h may be greater than 10 mm, preferably greater than 11 mm and/or less than 20 mm, preferably less than 15 mm In this instance, by way of example, the maximum distance h is substantially equal to 11.5 mm. Too small a height h may give rise to significant pressure drops in the aerodynamic tube 8, which may necessitate the use of a more powerful and therefore more voluminous turbomachine. For the same value of the distance between the aerodynamic tubes 8, as measured in the direction of alignment of the aerodynamic tubes, too great a height h limits the passage cross section between the aerodynamic tubes for the induced air flow. The total air flow directed toward the heat exchanger is therefore likewise reduced.

The first profile 42 here comprises a convexly curved part 50 of which the vertex defines the point of the first profile 42 that corresponds to the maximum distance h. The convexly curved part 50 may be positioned downstream of the opening 40 in the direction in which the flow of air is ejected. In particular, the convexly curved part 50 may be contiguous with the internal lip 40 b delimiting the opening 40.

Downstream of the convexly curved part 50 in the direction in which said flow of air is ejected through the opening 40, the first profile 42 of the aerodynamic tube 8 of the example of FIG. 12 comprises a first substantially rectilinear part 52. The second profile 44 comprises, in the example illustrated in FIG. 12, a substantially rectilinear part 48, preferably extending over the majority of the length of the second profile 44. In the example of FIG. 12, the length l of the first rectilinear part 52, as measured in a direction perpendicular to the longitudinal direction of the aerodynamic tube 8 and to the direction of alignment of the row of aerodynamic tubes, may be greater than or equal to 30 mm, preferably greater than or equal to 40 mm and/or less than or equal to 50 mm. A relatively long length for this first rectilinear part is desirable particularly in order to ensure guidance of the flow of air ejected from the opening 40, something which allows a greater amount of air to be drawn in. The length of this first rectilinear part is, however, limited on account of the corresponding bulkiness of the ventilation device and the consequences this has on the packaging of the ventilation device or of the heat-exchange module. In that case, the first rectilinear part 52 of the first profile 42 and the rectilinear part 48 of the second profile 44 may form a non-flat angle θ. The angle θ thus formed may notably be greater than or equal to 5°, and/or less than or equal to 20°, more preferably still, substantially equal to 10°. This angle made by the first rectilinear part 52 with respect to the rectilinear part 48 of the second profile 44 makes it possible to accentuate the expansion of the flow of air ejected by the opening 40 and experiencing the Coanda effect forcing it to follow the first profile 42, this accentuated expansion making it possible to increase the induced air flow. Too great an angle 0 does however carry the risk of preventing the Coanda effect from occurring, so that there is the risk that the flow of air ejected via the opening 40 might not follow the first profile 42 and, as a result, might not be oriented correctly toward the heat exchanger 2.

The first profile 42 may, as illustrated in FIG. 12, comprise a second rectilinear part 38 a, downstream of the first rectilinear part 52, in the direction in which the flow of air is ejected, the second rectilinear part 38 a extending substantially parallel to the rectilinear part 48 of the second profile 44. The first profile 42 may also comprise a third rectilinear part 54, downstream of the second rectilinear part 38 a of the first profile 42. The third rectilinear part 54 may make a non-flat angle with the rectilinear part 48 of the second profile 44. The third rectilinear part 54 may, as illustrated, extend substantially as far as a rounded edge connecting the third rectilinear part 54 of the first profile 42 and the rectilinear part 48 of the second profile 44. The rounded edge may define the trailing edge 38 of the transverse section of the aerodynamic tube 8.

The rectilinear part 48 of the second profile 44 extends in the example of FIG. 12 over the majority of the length c of the transverse section. This length c is measured in a direction perpendicular to the longitudinal direction of the aerodynamic tubes 8 and to the direction of alignment of the row of aerodynamic tubes 8. This direction corresponds, in the example of FIG. 12, substantially to the direction of flow of the induced air flow. In this first exemplary embodiment, the length c of the transverse section (or width of the aerodynamic tube 8) may be greater than or equal to 50 mm and/or less than or equal to 70 mm, preferably substantially equal to 60 mm. Specifically, the inventors have found that a relatively long length for the transverse section of the aerodynamic tube allows more effective guidance of the flow of air ejected by the opening 40 and the induced flow of air, which mixes with this flow of ejected air. However, too great a length of the transverse section of the aerodynamic tube 8 poses problems with the packaging of the ventilation device 2. In particular, the heat-exchange module may then become too bulky in relation to the space available in the motor vehicle in which it is intended to be mounted. The packaging of the heat-exchange module or of the ventilation device may also prove problematical in that case.

Furthermore, as illustrated in FIG. 12, the second rectilinear part 38 a of the first profile 42 and the portion 38 b of the rectilinear part 48 of the second profile 44 which faces it, are parallel. For example, the distance f between this second rectilinear part 38 a and the portion 38 b of the rectilinear part 48 of the second profile 44 may be greater than or equal to 2 mm and/or less than or equal to 10 mm, preferably less than or equal to 5 mm.

FIG. 12 also illustrates that the transverse section (or geometric section) of the aerodynamic tube 8 delimits a passage cross section S for the passage of the flow of air passing along the aerodynamic tube 8. This passage cross section S is defined here by the walls of the aerodynamic tube 8 and by the segment extending in the direction of alignment of the aerodynamic tubes 8 between the second profile 44 and the tip of the end 51 of the internal lip 40 b. This passage cross section may have a surface area greater than or equal to 150 mm², preferably greater than or equal to 200 mm², and/or less than or equal to 700 mm², preferably less than or equal to 650 mm². A passage cross section for the flow of air in the aerodynamic tube 8 makes it possible to limit the pressure drops which would result in the need to over-rate the panel fans used in order to obtain the desired rate of flow of air ejected via the opening 40. However, a large passage cross section results in the aerodynamic tube 8 being very bulky. Thus, for a fixed spacing of the aerodynamic tubes, a larger passage cross section carries the risk of detracting from the cross section for the passage of the induced air flow between the aerodynamic tubes 8, thus making it impossible to obtain a satisfactory total rate of flow of air directed toward the heat-transfer tubes 4.

In order to cause the least possible obstruction to the flow of air toward the heat-transfer tubes 4 and the fins, the ventilation device 2 equipped with such aerodynamic tubes 8 is advantageously arranged in such a way that each aerodynamic tube 8 faces the frontal face 4 f connecting the first 4 a and second 4 b planar walls of a corresponding heat-transfer tube 4. More particularly, the trailing edge 38 of each aerodynamic tube 8 is contained within the volume delimited by the first and second planar longitudinal walls of the corresponding heat-transfer tube 4.

As a preference, the second rectilinear part 38 a of the first profile and the rectilinear part 48 of the second profile 44 are respectively contained in the one same plane as the first planar longitudinal wall and the second planar longitudinal wall of the corresponding heat-transfer tube 4.

In particular, the distance f separating the second rectilinear part 38 a of the first profile 42 and the portion 38 b of the rectilinear part 48 of the second profile 44 that faces it, is substantially equal to the distance separating the first longitudinal wall and the second longitudinal wall of the heat-transfer tube 4 facing which the aerodynamic tube 8 is positioned. For example, this distance f is greater than or equal to 2 mm and/or less than or equal to 10 mm, preferably less than or equal to 5 mm.

In other embodiments, the distance f separating the second rectilinear part 38 a of the first profile 42 and the portion 38 b of the rectilinear part 48 of the second profile 44 that faces it, may, however, be less than the distance separating the first longitudinal wall and the second longitudinal wall of the heat-transfer tube facing which the aerodynamic tube 8 is positioned.

Two heat-transfer tubes 4 may be contained in the volume delimited by the air passage defined by two neighboring aerodynamic tubes 8. However, it is conceivable for just one heat-transfer tube 4, or else for three or four heat-transfer tubes 4 to be contained in this volume. Conversely, it is conceivable for one aerodynamic tube 8 to be positioned facing each heat-transfer tube 4.

In the examples of FIGS. 13, 14 and 15, the aerodynamic ducts 8 are substantially rectilinear, mutually parallel, and aligned in such a way as to form a row of aerodynamic tubes 8. However, the first and second profiles 42, 44 of each aerodynamic tube 8 are, in these examples, symmetrical with respect to a plane C-C, or chord plane, passing through the leading edge 37 and the trailing edge 38 of each aerodynamic tube 8.

Because the first and second profiles 42, 44 are symmetrical, each of these profiles 42, 44 is provided with an opening 40. Thus, at least one first opening 40 is produced on the first profile 42, which is configured so that a flow of air exiting the first opening 42 flows along at least a part of the first profile 42. Similarly, at least one second opening 40 is present on the second profile 44, which is configured so that a flow of air exiting the second opening 40 flows along at least a part of the second profile 44. As with the example of FIG. 12, this can be achieved here by making use of the Coanda effect.

For the same reasons as those given for the example of FIG. 12, the distance c between the leading edge 37 and the trailing edge 38 may also, in these examples, be greater than or equal to 50 mm and/or less than or equal to 80 mm. In particular, the length c may be equal to 60 mm.

The openings 40 are analogous to those of the example of FIG. 12. In particular, the distance e separating the internal 40 b and external 40 a lips of each opening 40 can be greater than or equal to 0.3 mm, preferably greater than or equal to 0.5 mm, more preferably greater than or equal to 0.7 mm, and/or less than or equal to 2 mm, preferably less than or equal to 1.5 mm, more preferably less than or equal to 0.9 mm, and even more preferably less than or equal to 0.7 mm.

The fact that the profiles 42, 44 are symmetrical relative to the chord plane C-C passing through the leading edge 37 and the trailing edge 38 of the aerodynamic tube 8 means that the obstruction of the flow of air between the ventilation device 2 and the heat-transfer tubes 4 can be limited, whilst creating more air passages in the volume available in front of the heat-transfer tubes 4.

In other words, unlike in the embodiment of FIG. 12, an air passage that entrains ambient air is created between each pair of neighboring aerodynamic tubes 8, produced according to one of FIGS. 13 to 15.

The spacing between two neighboring aerodynamic tubes 8 may, in this case, be greater than or equal to 15 mm, preferably greater than or equal to 20 mm, more preferably still, greater than or equal to 23 mm and/or less than or equal to 30 mm, preferably less than or equal to 25 mm, more preferably still, less than or equal to 27 mm. Specifically, if the spacing between the aerodynamic tubes 8 is smaller, the rate at which the induced air flows finds itself limited by the small passage section between the aerodynamic tubes. On the other hand, if the spacing is too great, the ejected flow of air is unable to create an induced air flow across the entire spacing between the neighboring aerodynamic tubes.

The spacing between two neighboring aerodynamic tubes 8 may notably be defined as the distance between the center of the transverse section of two neighbouring aerodynamic tubes 8 or, more generally, as being the distance between a point of reference on a first aerodynamic tube 8 and the point, corresponding to the point of reference, on the closest aerodynamic tube 8. The point of reference may notably be one of: the leading edge 37, the trailing edge 38, the vertex of the convexly curved part 50.

The distance between the aerodynamic tubes 8 and the heat-transfer tubes 4 may notably be chosen greater than or equal to 5 mm, preferably greater than or equal to 40 mm, and/or less than or equal to 150 mm, preferably less than or equal to 100 mm. Specifically, the peak velocity of the velocity profile of the air in the vicinity of the profile has a tendency to decrease with increasing distance away from the opening 40 in the aerodynamic tube. The absence of a peak indicates uniform mixing of the flow of air ejected by the opening 40 and the induced airflow. It is preferable for such uniform mixing to be achieved before the flow of air reaches the aerodynamic tubes. This is because a nonuniform flow of air incident on the heat-transfer tubes does not allow optimal cooling of the heat-transfer tubes and leads to greater pressure drops. However, the distance between the aerodynamic tubes and the heat-transfer tubes is preferably contained so as to limit the space occupied by the cooling module.

In the example illustrated in FIG. 13, the first and second profiles 42, 44 of the aerodynamic tube 8 converge toward the trailing edge 38 such that the distance separating the first and second profiles 42, 44 decreases strictly in the direction of the trailing edge 38 from a point on these first and second profiles 42, 44 that corresponds to the maximum distance h between these two profiles, these points on the first and second profiles 42, 44 being downstream of the openings 40 in the direction in which the flow of air ejected via the opening 40 flows. As a preference, the first and second profiles 42, 44 each form an angle of between 5 and 10° with the chord C-C of symmetry of the transverse section of the aerodynamic tube 8.

As a result, unlike in the example of FIG. 12, the aerodynamic profile of FIG. 13 does not contain a portion delimited by parallel opposing planar first and second walls.

This offers the advantage of limiting the drag along the aerodynamic profile of the aerodynamic tube 8.

For example, the maximum distance h between the first profile 42 and the second profile 44 may be greater than or equal to 10 mm and/or less than or equal to 30 mm. In particular, this maximum distance h may be equal to 11.5 mm.

In the example illustrated in FIG. 14, the trailing edge 38 is formed by the vertex joining two symmetrical rectilinear portions 60 of the first profile 42 and of the second profile 44 of each aerodynamic tube 8. In the variant of FIG. 14, the trailing edge 38 is the point of the transverse section of the aerodynamic tube 8 that is situated closest to the heat exchanger. In other words, the angle a formed by the two rectilinear portions 60 is less than 180°, notably less than 90°.

On the other hand, in the variant of FIG. 15, the trailing edge 38 is positioned between the two rectilinear portions 38 a, 38 b of the first and second profiles 42, 44. In other words, the angle α formed by the two rectilinear portions 60 is here greater than 90°, notably greater than 180°.

The invention is not limited to the embodiments presented, and further embodiments will be clearly apparent to a person skilled in the art. In particular, the various embodiments can be combined, provided they are not contradictory. 

1. An impeller for a tangential fan to be fitted to a motor vehicle, the impeller extending chiefly in the direction of a longitudinal axis of the impeller, the impeller comprising: a plurality of blades distributed in stages along said longitudinal axis of the impeller, each stage comprising a plurality of blades angularly distributed about said longitudinal axis of the impeller, the blades of each stage of blades being equally angularly distributed about said longitudinal axis of the impeller, in which impeller the blades of a first stage of blades are angularly offset from the blades of at least a second stage of blades.
 2. The impeller as claimed in claim 1, wherein the blades of the first stage of blades are angularly offset from the blades of the two stages of blades neighboring said first stage of blades.
 3. The impeller as claimed in claim 2, wherein the blades of each first stage of blades are angularly offset from the blades of the two stages of blades neighboring each first stage of blades.
 4. The impeller as claimed in claim 1, wherein the blades of the first stage of blades are angularly offset from the blades of the at least one second stage of blades by an angular offset corresponding to the thickness of the blades of the first stage of blades and/or of the second stage of blades.
 5. The impeller as claimed in claim 1, wherein the blades of the first stage of blades are angularly offset from the blades of the at least one second stage of blades by an angular offset equal to half the angular spacing between the blades of the first stage of blades and/or of the at least one second stage of blades.
 6. The impeller as claimed in claim 1, wherein the blades of said first stage of blades are angularly offset from all the blades of all the other stages of blades.
 7. The impeller as claimed in claim 6, wherein the blades of the each stage of blades are angularly offset from all the blades of all the other stages of blades.
 8. A tangential fan configured to be fitted to a motor vehicle comprising: a blower housing defining a substantially cylindrical housing; an electric motor; and an impeller housed in the substantially cylindrical housing and configured to be driven in rotation by the electric motor, the impeller comprising: a plurality of blades distributed in stages along said longitudinal axis of the impeller, each stage comprising a plurality of blades angularly distributed about said longitudinal axis of the impeller, the blades of each stage of blades being equally angularly distributed about said longitudinal axis of the impeller, in which impeller the blades of a first stage of blades are angularly offset from the blades of at least a second stage of blades.
 9. A ventilation device for a motor vehicle heat-exchange module, comprising: a tangential fan having a blower housing defining a substantially cylindrical housing, an electric motor, and an impeller housed in the substantially cylindrical housing and configured to be driven in rotation by the electric motor, the impeller comprising: a plurality of blades distributed in stages along said longitudinal axis of the impeller, each stage comprising a plurality of blades angularly distributed about said longitudinal axis of the impeller, the blades of each stage of blades being equally angularly distributed about said longitudinal axis of the impeller, in which impeller the blades of a first stage of blades are angularly offset from the blades of at least a second stage of blades; and a plurality of tubes able to be supplied with air flow by the tangential fan, each tube having at least one ejection opening for a flow of air passing along the tube.
 10. A heat-exchange module for a motor vehicle comprising: a heat-exchange device; and a ventilation device as claimed in claim 9, which is configured to generate a flow (F1) of air through the heat-exchange device. 